Construction of a quaternary ammonium salt platform with different alkyl groups for antibacterial and biosensor applications

An electrochemical platform was designed using biocompatible quaternary ammonium salts containing alkyl groups with different chain lengths as electrode materials for visible protein immobilization on a glassy carbon (GC) electrode. The electrode was constructed using a simple self-assembly method relying on the electrostatic interaction between negatively charged hemoglobin (Hb) and positively charged quaternary ammonium materials. The Hb/quaternary ammonium salts/GC assembly exhibited excellent catalytic and electrochemical activities. Additionally, the structure-function properties of the quaternary ammonium salts on the electrochemical behavior of Hb was systematically investigated for various alkyl chain lengths between monomer and polymeric structures. Meanwhile, the corresponding bactericidal activities of the monomers and related polymers were evaluated by determining the minimum bactericidal concentration (MBC), minimum inhibitory concentration (MIC), and inhibitory zone diameters against bacteria. The results of these studies demonstrated that the quaternary ammonium monomers not only immobilized more proteins, but also displayed better antibacterial activity as alkyl chain length increased. Moreover, polymers possessed higher antimicrobial activities than their monomeric counterparts. However, the efficiency of the direct electron transfer process and the antibacterial properties of long-chain polymers were limited because they were prone to aggregation and blistering. In summary, the present results provide convenient access to direct electrochemistry using an immobilized redox protein. Furthermore, the potential to use the obtained materials in the construction of third-generation electrochemical biosensors was evaluated.